A polygon determined by the distance between
successive vertices and the angles formed by
each three successive vertices. In other
words, a polygon specified by "turtle
graphics": go straight ahead x1 units; turn by
angle a1; go straght ahead x2 units; turn by
angle a2; etc. The polygon will be centered at
the centroid of its vertices.

The first argument is a list of vertexangles, giving the angle at each vertex
from the previous vertex to the next. The
first angle in the list is the angle at the
second vertex; the first edge always starts
out heading in the positive y direction from
the first vertex.

The second argument is a list of distances
between successive vertices.

To construct an n-gon, use a list of n-2
angles and n-1 edge lengths. Extra angles or
lengths are ignored.

Specify a star polygon by a "skip". A skip of
1 indicates a normal polygon, where edges go
between successive vertices. A skip of 2 means
that edges will connect every second vertex,
skipping one in between. Generally, a skip of
n means that edges will connect every nth
vertex.

Create a generalized starpolygon. The StarOpts are used
to determine in which order the given vertices should be
connected. The intention is that the second argument of type
[P2] could be generated by a call to polygon, regPoly, or
the like, since a list of vertices is TrailLike. But of course
the list can be generated any way you like. A PathR2 is
returned (instead of any TrailLike) because the resulting path
may have more than one component, for example if the vertices are
to be connected in several disjoint cycles.

Function graphs

These functions are used to implement star, but are exported on
the offchance that someone else finds them useful.